As an oscillator that uses a crystal resonator, for example, an OCXO (Oven Controlled Xtal Oscillator), which is an oscillator with an oven, is configured to heat an atmosphere in which the crystal resonator is placed to a constant temperature with a heater such that the temperature of the crystal resonator is not affected by an external temperature variation. As a technique that aimed to improve temperature control accuracy of the heater, there is known a method for using two crystal resonators as temperature sensors to obtain a signal value corresponding to a temperature detection value calculated by using a frequency difference between the two crystal resonators, and controlling an output power of the heater on the basis of this signal value (Patent Document 1).
On the other hand, a frequency relative to a temperature of an oscillator, for example in a system that transmits a radio wave from a base station to a terminal, requires a much higher stability not only in the base station but even in a relay station. Patent Document 2 discloses that a temperature compensation type crystal controlled oscillator 1 is driven by using a voltage regulator, however, a configuration of the present invention is not disclosed.